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Full text of "IS 516: Method of Tests for Strength of Concrete"

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Disclosure to Promote the Right To Information 

Whereas the Parliament of India has set out to provide a practical regime of right to 
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in order to promote transparency and accountability in the working of every public authority, 
and whereas the attached publication of the Bureau of Indian Standards is of particular interest 
to the public, particularly disadvantaged communities and those engaged in the pursuit of 
education and knowledge, the attached public safety standard is made available to promote the 
timely dissemination of this information in an accurate manner to the public. 



Mazdoor Kisan Shakti Sangathan 
"The Right to Information, The Right to Live" 



Jawaharlal Nehru 
'Step Out From the Old to the New" 



IS 516 (1959) : Method of Tests for Strength of Concrete 
[CED 2: Cement and Concrete] 



Satyanarayan Gangaram Pitroda 
Invent a New India Using Knowledge 




5fR TT^ ^TT <sMHI | *ft ^fft ^TRT ^ff ^TT ^T^fT )f 

Bhartrhari — Nltisatakam 
"Knowledge is such a treasure which cannot be stolen" 





BLANK PAGE 




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*?W!& 



PROTECTED BY COPYRIGHT 



IS : 516-1959 

( Reaffirmed 2004 ) 



Indian Standard 

METHODS OF TESTS FOR 
STRENGTH OF CONCRETE 



Kighteenth Reprint JUNE 2006 
( Incorporating Amendment No l and Including Amendment No 2 ) 



UDC 666.97.620 17 



to Copyright 1975 
BUREAU OF INDIAN STANDARDS 

MANAK UHAVAN 9 RAHAIH'R SHAH ZA1 \R MARO 
N J W 1)1 1 III 1 10002 

Gr 6 December 1959 



IS: 516 -1959 



Indian Standard 

METHODS OF TESTS FOR 
STRENGTH OF CONCRETE 



Cement and Concrete Sectional Committee, BDC 2 

Chairman 
Shri R. A. Nadirshah The Concrete Association of India, Bombay, and 

the Institution of Engineers I India ), Calcutta 

Member* 
Shri Baleshwar Nath Central Board oi Irrigation <S Power ( Ministry ol 

Irrigation & Power ) 
Shri N. H. Bhagwanani Engincer-in-Chief's Branch, Army Headquarters. 

Shri N. D. Dabtary Bombay State Hood Transport Corporation. Bomba> 

Shri P. I„ Das Directorate General ot Supplies & Disposals 

( Ministry of Works, Housing & Supply ) 
Director Central Building Research Institute (CSIR), 

Roorkce 
Shri C. H. Khadilka* ( Alternate ) 
Shki C: L. Handa Directorate ol Designs., Bhakra Dam, N'ew Delhi 

Shri P. S. BhatkacaR (Alternate) 
Or R. R. Hattiangadi The Associated Cement Companies Ltd, Bomba\ 

Shri V. N. Pai ( Afu-rmtte ) 
Shri P. C. Hazr* Geological Survev of India, Calcutta 

0" R. C. Hook Central Water & Tower Commission ( Ministry .>i 

Irrigation & Power ) 
Shri George Oommen ( Alternate ) 
Shri S. B. Joshi S. B. Joshi * Co, Bombax 

Shri S. R. Mbhma Central Road Research Institute iCSIN), New 

Delhi 
Shhi S. N. Mukerji Government Test House, Calcutta 

Shri K. K. Chatterjee {Alternate) 
SKRI E. P. Nicolaides Gammon India Ltd, Bombav. and Indian Roads 

Congress, New Delhi 
KKPRKbLN fATfVE Martin Burn Ltd, Calcutta 

Shri J. M. Kijhwani Central Public Works Department 

Shri M. S. Bhatia ( Alternate ) 
Shki Nihar Chandra Roy Dalmia Cement { Bharat ) Ltd, Calcutta 

Shri A. K. Chakrav\rk [Alternate) 
Shri Sakvp Singh National Buildings Uiganisation ( Ministry of 

Works, Housing & Suppl) * 
Deputy Director ( Material ) (Alttrnale) 

( Continued on page 2 ) 

BUREAU OF INDIAN STANDARDS 

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG 
NEW DELHI 110002 



IS: 516 -1959 



l Continued from page 1 ) 

Shri II P. Siniia Roads Wing, Ministry of Transport St Communica- 

tions 
Sum J. M. Tubman [Alternate) 
Shki K. C, Suou Research, Design & Standardization Organization 

( Ministry of Railways ) 
Shki S. S. Varma ( Alternate ) 
D« I.ai ('. Vhhman I Ex-officm ) Director, Indian Standards Institution 

Secretary 
shki (. S fiUNDRAMtKHAKA Deputy Director ( BIdg ), Indian Standards Insti- 

tution 

Concrete Subcommittee, BDC 2:2 

{ nnvt-Hct 
Smrj S. B Jiishi S. H Joshi tk Co, Bombav 

Mr nihil • 
Shki K. K Aniia The Associated Cement Companies Ltd., Bombay 

Shki N*. II. Bii \r.\v \\ \ni Kngineer-in-Chief's Branch, Army Headquarters 

Shri M. S Bhaiia Central Public Works Department 

Sum T S Vi-.uaciki i Alternate ) 
Dikkctor Engineering Research Laboratories, Hyderabad 

Shri P. ('. Hazra Geological Survey of India, Calcutta 

Dr H. <\ Hoon Central Water & Power Commission ( Ministry of 

Irrigation & Power ) 
shki ( . L. N. Iykni,an I'hc Concrete Association of India, Bombay 

Shri S. V. Nati- Public Works Department, Bombay 

Shri C C. Purl ( Alternate ) 
Shri K. P. N'icolaides Gammon India Ltd., Bombay 

Dr K 1.. Rao Central Water & Power Commission (Ministry of 

Irrigation & Power ) 
Shri Sahup Singh National Buildings Organisation (Ministry of 

Works, Housing & Supply ) 
Shri K. Kama V\km*n {Alternate) 
Shri H. P. Sinha Roads Wing, Ministry of Transport & Communica- 

tions 
Shri K. (.'. Soop Research, Design & Standardization Organization 

( Ministry of Railways ) 



AMENDMENT NO. 2 JULY 1991 

TO 

IS 516 : 1959 METHODS OF TESTS FOR 
STRENGTH OF CONCRETE 

( Page 6, clause 2.9.1 ) — Substitute the following for the existing 
clause: 

1.9.1 Cube Moulds — The mould shall be of 150 mm size conforming 
to IS 10086 : 1982*. * 

( Page 6 ) — Insert the following foot-note at the bottom: 

'•Specification for moulds for use in tests of cement and concrete.' 

( Page 7, clause 2.9.2 ) — Except the last sentence, substitute the 
following for the existing matter: 

'The cylindrical moulds shall be of 1 50 mm diameter and 300 mm height 
conforming to IS 10086 : 1982*.' 

( Page 7, clause 2.9.3 ) — Substitute the following for the existing 
clause: 

'2.9.3 Tamping Bar — The tamping bar shall conform to 6.1(a) of 
IS 10086 : 1982*.' 

( Page 7 ) — Insert the following foot-note at the bottom: • 

'♦Specification for moulds for use in tests of cement and concrete.' 

( Pages 15 and 16, clause 7.4.1) — Substitute the following for the 
existing clause: 

'7.4.1 Beam Moulds — The beam moulds shall conform to IS 10086 : 
1982*. 

In assembling the mould for use, the joints between the sections of the 
mould shall be thinly coated with mould oil and a similar coating of 
mould oil shall be applied between the contact surfaces of the bottom of 
the mould and the base plate in order to ensure that no water escapes 
during the filling. The interior faces of the assembled mould shall be 
thinly coated with mould oil to prevent adhesion of the concrete.' 

( Page 15 ) — Insert the following foot-note at the bottom: 

'•Specification for moulds for use in tests of cement and concrete.' 

( Page 16, clause 7.4.2 ) — Substitute the following for the existing 
clause: 

'7.4.2 Tamping Qor — The tamping bar shall contorm to 6.1(b) of 
IS 10086 : 1982*.' 



( CED 2 ) 



Printed ■< Simco Printing Prna, D*lhi. India 



IS: 516 -1959 

Indian Standard 

METHODS OF TESTS FOR 
STRENGTH OF CONCRETE 

0. FOREWORD 

0.1 This Indian Standard was adopted by the Indian Standards Institution 
on 10 November 1959, after the draft finalized by the Cement and 
Concrete Sectional Committee had been approved by the Building Division 
Council. 

0.2 Testing plays an important role in controlling the quality of cement 
concrete work. Systematic testing of the raw materials, the fresh con- 
crete and the hardened concrete is an inseparable part of any quality 
control programme for concrete which helps to achieve higher efficiency 
of the materials used and greater assurance of the performance of the 
concrete in regard to both strength and durability. The test methods 
used should be simple, direct and convenient to apply. This standard 
has been prepared with this object in view and provides a guide to the 
determination of compressive strength, flexural strength and modulus of 
elasticity of concrete. Sampling and analysis of concrete have been covered 
separately in IS: 1199-1959 Methods of Sampling and Analysis of Concrete. 
0.3 The Sectional Committee responsible for the pieparation of this stan- 
dard has taken into consideration the views of concrete specialists, testing 
authorities, consumers and technologists and has related the standard to 
the practices followed in the country in this field. The need for inter- 
national co-ordination between standards prevailing in different countries 
of the world has also been recognized. These considerations led the Sec- 
tional Committee to derive assistance from the published standards and 
publications of the following organizations : 

British Standards Institution 

American Society for Testing Materials 

American Concrete Institute 

Canadian Engineering Standards Association 

Research, Design & Standardization Organization, Ministry 

of Railways, Government of India 
The Concrete Association of India 
0.4 The Indian Standard Methods of Sampling and Analysis of Concrete 
(IS: 1199-1959) is a necessary adjunct to this standard. Besides, this 
standard requires reference to the following Indian Standards : 

•IS : 269-1958 Specification for Ordinary, Rapid-Hardening and 
Low Heat Po rtland Cement (Revised) 

•Since revised. 



IS: 516 -1959 

*IS : 383-1952 Specification for Coarse and Fine Aggregates from 
Natural Sources for Concrete 

tIS: 455-1953 Specification for Portland Blastfurnace Slag 
Cement 

* IS -.456-1957 Code of Practice for Piain and Reinforced Con- 
crete for General Bitlding Construction (Revised) 

•IS : 460-1953 Specification for Test Sieves 

0.4.1 Wherever a reference to any standard mentioned in 0.4, except 
IS: 460-1953, appears in this standard, it shall be taken as a reference to 
the latest version of the standard. 

0.5 In pursuance of the decision of the Government of India to introduce 
a uniform system of weights and measures throughout the country based 
on the metric system, in this standard, all dimensions and values have 
been given in metric units only. It is hoped that this step will facilitate 
the change-over to the metric system by the industry more expeditiously. 
0.6 For the purpose of deciding whether a particular requirement of this 
standard is complied with, the final value observed or calculated, expres- 
sing the result of a test or analysis, shall be rounded off in accordance 
with'IS: 2-1949 Rules for Rounding Off Numerical Values. The number 
of significant places retained in the rounded off value should be the same 
as that of the specified value in this standard. 

0.7 This standard is intended chiefly to cover the technical provisions 
relating to the testing of concrete, and it does not include all the necessary 
provisions of a contract. 



1. SCOPE 

1.1 This standard covers tests for the determination of compressive 
strength, ftexural strength and modulus of elasticity of cement concrete. 

2. MAKING AND CURING COMPRESSION 
TEST SPECIMENS IN THE LABORATORY 

2.1 This clause specifies the procedure for making and curing compression 
test specimens of concrete in the laboratory where accurate control of the 
quantities of materials and test conditions are possible and where the 
maximum nominal size of aggregate docs not exceed 38 mm. The method 
is specially applicable to the making of preliminary compression tests 
to ascertain the suitability of the available materials or to determine 
suitable mix proportions. 

2.2 Sampling of Material* - Representative samples of the materials 
of concrete for use i n the particular concrete construction work shall be 

~~ •Sinle "revised. 
f Second revision issued in I9d7. 4 

' Second revision issued in 19M. 



IS: 516- 1959 

obtained by careful sampling. Test samples of cement shall be made up 
of a small portion taken from each of a number of bags on the site. Trst 
samples of aggregate shall be taken from larger lots by quartering. 

2.3 Preparation of Materials - All materials shall be brought to room 
temperature, preferably 27 +3C before commencing the tests. 

The cement samples, on arrival at the laboratory, shall be thoioughly 
mixed dry either by hand or in a suitable ini\er in such a manner as to 
ensure the greatest possible blending and uniformity in the material, c:\n- 
being taken to avoid the intrusion of foreign matter. The cement shall 
then be stored in a dry place, preferably in air-tight metal containers. 

Samples of aggregates for each batch of concrete shall be of the desired 
grading and shall be ir. an ait-dried condition. In general, the aggregate 
shall be separated into fine and coarse fractions and recombined for each 
concrete batch in such a manner as to produce the desired grading. Is 
Sieve 480 shall be normally used for separating the fine and coarse frac- 
tions, but where special gradings are being investigated, both tine and 
coarse fractions shall be further separated into different sizes. 

2.4 Proportioning — The proportions of the materials, including water, 
in concrete mixes used for determining the suitability of the materials 
available, shall be similar in all respects to those to be employed in the 
A'ork. Where the proportions of the ingredients of the concrete as used 
jn the site are to be specified by volume, they shall be calculated trorn 
the proportions by weight used in the test cubes and the unit wtiehis of 
the materials. 

2.5 Weighing The quantities of cement, each si/.e of aggregate, and 
water for each batch shall be determined by weight, to an accuracy of 
0-1 percent of the total weight of the batch. 

2.6 Mixing Concrete - The concrete shall be mixed by hand, or pre- 
ferably, in a laboratory batch mixer, in such a manner as to avoid loss of 
water or other materials. Each batch of concrete shall be of such a sue 
as to leave about 10 percent excess after moulding the desired number of 
test specimens. 

2.6.1 Machine Mixing —When the mixing drum is chaigcd by a powci 
loader, all the mixing water shall be introduced into the drum bef<ue the 
solid materials; the skip shall be loaded with about one-hall ot the coarse 
aggregate, then with the fine aggregate, then with the cement and finally 
with the remaining coarse aggregate on top. (If all in-aggiegate is used, 
the skip shall be loaded first with about one-half of the aggregate then 
with the cement and finally with the remaining aggregate on top.) 
Where the mixing drum is hand-loaded it shall be chaiged with the dry 
materials in a similar manner, and the water shall be added immediately 
before the .rotation of the drum is started. The period of mixing shall 



IS: 516 -1959 

be not less than 2 minutes after all the materials are in the drum, and shall 
continue till the resulting concrete is uniform in appearance. When using 
pan mixers, the concrete shall be heaped together before sampling. 

2.6.2 Hand Mixing-- The concrete batch shall be mixed on a water- 
tight, non-absorbent platform with a shovel, trowel or similar suitable 
implement, using the following procedure: 

a) The cement and fine aggregate shall be mixed dry until the mixture 
is thoroughly blended and is uniform in colour, 

b) The coarse aggregate shall then be added and mixed with the 
cement and fine aggregate until the coarse aggregate is uniformly 
distributed throughout the batch, and 

c) The water shall then be added and the entire batch mixed until 
the concrete appears to be homogeneous and has the desired con- 
sistency. If repeated mixing is necessary, because of the addition 
of water in increments while adjusting the consistency, the batch 
shall be discarded and a fresh batch made without interrupting 
the mixing to make trial consistency tests. 

2.7 Workability — Each batch of concrete shall be tested for consistency 
immediately after mixing, by one of the methods described in IS: 
1199-1959. Provided that care is taken to ensure that no water or other 
material is lost, the concrete used for the consistency tests may be re- 
mixed with the remainder of batch before making the test specimens. 
The period of re-mixing shall be as short as possible yet sufficient to produce 
a homogeneous mass. 

2.8 Size of Test Specimens - Test specimens cubical in shape shall be 
15 X IS x 15 cm. If the largest nominal size of the aggregate does not 
exceed 2 cm, 10 cm cubes may be used as an alternative. Cylindrical test 
specimens shall have a length equal to twice the diameter. They shall 
be 15 cm in diameter and 30 cm long. Smaller test specimens shall have 
a ratio of diameter of specimen to maximum size of aggregate of not less 
than 3 to 1, except that the diameter of the specimen shall be not less 
than 7-5 cm for mixture? containing aggregate more than 5 percent of 
which is retained on IS Sieve 480. 

2.9 Moulds 

2 9.1 Cube Moulds — The mould shall be ol metal, preferably steel or 
cast iron, and stout enough to prevent distortion. It shall be constructed 
in such a manner as to facilitate, the removal of the moulded specimen 
without damage, and shall be s<> machined that, when it is assembled ready 
for use. the dimensions and internal faces shall be accurate within the 
following limits: 

The height of the mould and the distance between opposite faces 
shall be the specified size + 02 mm. The angle between adjacent 



18:516-1959 

internal faces and between internal faces and top and bottom planes 
of the mould shall be 90° + 0-5°. The interior faces of the mould 
shall be plane surfaces with a permissible variation of 0-03 mm. 
Each mould shall he provided with a metal base plate having a plane 
surface. The base plate shall be of such dimensions as to support 
the mould during the filling without leakage and it shall be preferably 
attached to the mould by springs or screws. The parts of the mould 
when assembled shall be positively and rigidly held together, and 
suitable methods of ensuring this, both during the filling and on 
subsequent handling of the filled mould, shall be provided. 

2.9.1.1 In assembling the mould for use, the joints between the 
sections of mould shall be thinly coated with mould oil and a similar 
coating of mould oil shall be applied between the contact surfaces of the 
bottom of the mould and the base plate in order to ensure that no water 
escapes during the filling. The interior surfaces of the assembled mould 
shall be thinly coated with mould oil to prevent adhesion of the concrete 

2.9.2 Cylinders — The cylindrical mould shall be of metal which shall 
be not less than 3 mm thick. Each mould shall be capable of being opened 
longitudinally to facilitate removal of the specimen and shall be provided 
with a means of keeping it closed while in use. The ends shall not depai t 
from a plane surface, perpendicular to the axis of the mould, by more than 
0-05 mm. When assembled ready for use, the mean internal diameter of 
the mould shall be 15-0 cm ±0-2 mm and in no direction shall the internal 
diameter be less than 14-95 cm or more than 15-05 cm. The height shall 
be 30-0 cm + 0-1 cm. Each mould shall be provided with a metal base 
plate, and with a capping plate of glass or other suitable material. The 
base plate and the capping plate shall be at least 6-5 mm thick, and such 
that they do not depart from a plane surface by more than 0-02 mm. 
The base plate shall support the mould during filling without leakage and 
■diall be rigidly attached to the mould. The mould and base plate shall 
be coated with a thin film of mould oil before use, in order to prevent 
adhesion of the concrete. 

2.9.3 Tamping Bar — The tamping bar shall be a steel bar 16 mm in 
diameter, 0-6 m long and bullet pointed at the lower end. 

2.10 Compacting - The test specimens shall be made as soon as prac- 
ticable after mixing, and in such a way as to produce full compaction ol 
the concrete with neither segregation nor excessive laitance. The con- 
crete shall be filled into the mould in layers approximately 5 "cm deep. 
In placing each scoopful of concrete, the scoop shall He moved around the 
top edge ot the mould as the concrete slides from it, m order to ensure a 
symmetrical distribution of the concrete within the mould. Each layer 
shall be compacted either by hand or by vibration as described below 
(see 2.10.1 and 2.10.2). After the top layer has been compacted, the 



IS: 516 -1959 

surface of the concrete shall be finished level with the top of the mould, 
using a trowel, and covered with a glass or metal plate to prevent 
evaporation. 

2.10.1 Compacting by Hand —When compacting by hand, the stan- 
dard tamping bar shall be used and the strokes of the bar shall be distri- 
buted in a uniform manner over the cross-section of the mould. The 
number of strokes per layer required to produce specified conditions will 
vary according to the type of concrete. For cubical specimens, in no 
case shall the concrete be subjected to less than 35 strokes per layer for 
15 cm cubes or 25 strokes per layer for 10 cm cubes. For cylindrical speci- 
mens, the number of strokes shall not be less than thirty per layer. The 
strokes shall penetrate into the underlying layer and the bottom layer 
shall be rodded throughout its depth. Where voids are left by the tamp- 
ing bar, the sides of the mould shall be tapped to close the voids. 

2.10.2 Compacting by Vibration — When compacting by vibration, each 
layer shall be vibrated by me?ns of an electric or pneumatic hammer or 
vibrator or by means of a suitable vibrating table until the specified con- 
dition is attained. 

Note — The mode and quantum of vibration of the laboratory specimen shall 
be as nearly the s.mic as those adopted in actual connrtinR operations. 

2.1 1 Capping Specimens — The ends of all cylindrical test specimens 
that are not plane within 0-05 mm shall be capped. Capped surfaces 
shall not depart from a plane by more than 005 mm and shall be approxi- 
mately at right angles to the axis of the specimens. The planeness of the 
cap shall be checked by means of a straight edge and feeler gauge, making 
a minimum of three measurements on different diameters. Caps shall be 
made as thin as practicable and shall not flow or fracture when the specimen 
is tested. Capping shall be carried out according to one of the following 
methods. 

2.11.1 Neat Cement — Test cylinders may be capped with a thin layer 
of stiff, neat Portland cement paste after the concrete has ceased settling 
in the moulds, generally for two to four hours or more after moulding. 
The cap shall be formed by means of glass plate not less than 6-5 mm in 
thickness or a machined metal plate not less than 13 mm in thickness and 
having a minimum surface dimension at least 25 mm larger than the dia- 
meter of the mould. It shall be worked on the cement paste until its 
lower surface rests on the top of the mould. The cement for capping shall 
be mixed to a stiff paste for about two to four hours before it is to be 
used in order to avoid the tendency of the cap to shrink. Adhesion of 
paste to the capping plate may be avoided by coating the plate with a 
thin coat of oil or grease. 

2.11.2 Sulphur -- Just prior to testing, the cylindrical specimens may be 
capped with a sulphur mixture consisting of 2 or 3 parts sulphur to 1 part 
of inert filler, such as fire-clay. . The specimens shall be securely held in a 

8 



18:516-1959 

special jig so that the caps formed have true plane surfaces. Care shall be 
taken to ensure that the sulphur compound is not over-heated as it will 
not then develop the required compressive strength. Sulphur caps shall be 
allowed to harden for at least 2 hours before applying the load. 

2.11.3 Hard Plaster — Just prior to testing, specimens may be capped 
with hard plaster having a compressive strength of at least 420 kg/sq cm 
in one hour. Such plasters are generally available as proprietory material. 
The cap shall be formed by means of a glass plate not less than 13 mm in 
thickness, having a minimum surface dimension at least 25 mm larger than 
the diameter of the mould. The glass plate shall be lightly coated with 
oil to avoid sticking. 

Note Ordinary plaster of p.-iris will not serve the purpose of the capping 
materia! duo to itt low compressive stri-n^Ui 

2.11.4 As soon as possible after the concrete is mixed, a mortar shall 
be gauged using a cement similar to that used in the concrete and sand 
which passes IS Sieve 30 but is retained on IS Sieve 15. The mortar shall 
have a water/cement ratio not higher than that of the concrete of which 
the specimen is made, and shall be of a stiff consistence. If an excessively 
wet mix of concrete is being tested, any free water which has collected 
on the surface of the specimen shall be removed with a sponge, blotting 
paper or other suitable absorbent material before the cap is formed. The 
mortar shall then be applied firmly and compacted with a trowel to a 
slightly convex surface above the edges of the mould, after which the 
capping plate shall be pressed down on the cap with a rotary motion uatil 
it makes complete contact with the rim of the mould. The plate shall 
be left in position until the specimen is removed from the mould. 

2.12 Curing — The test specimens shall be stored in a place, free from 
vibration, in moist air of at least 90 percent relative humidity and at a 
temperature of 27° + 2°C for 24 hours ± \ hour from the time of addition 
of water to the dry ingredients. After this period, the specimens shall be 
marked and removed from the moulds and, unless required for test within 
24 hours, immediately submerged in clean, fresh water or saturated lime 
solution and kept there until taken out just prior to test. The water or 
solution in which the specimens are submerged shall be renewed every 
seven days and shall be maintained at a temperature of 27° + 2°C. The 
specimens shall not be alloweo to become dry at any time until they have 
been tested. 

3. MAKING AND CURING COMPRESSION TEST 
SPECIMEN IN THE FIELD 

3.1 This clause deals with the procedure for making and curing compres- 
sion test specimens of concrete sampled during the progress of construction 
where the nominal maximum size of the aggregate does not exceed 38 mm. 



IS: 516- 1959 

3.2 Size of test specimen, apparatus to be used and procedure to prepare 
specimens shall be the same as specified in 2. 

3.3 Curing — The test specimens shall be stored on the site at a place 
free from vibration, under damp matting, sacks or other similar material 
for 24 hours ± £ hour from the time of adding the water to the other 
ingredients. The temperature of the place of storage shall be within the 
range of 22° to 32°C. After the period of 24 hours, they shall be marked 
for later identification, removed from the moulds and, unless required for 
testing within 24 hours, stored in clean water at a temperature of 24° to 
30°C until they are transported to the testing laboratory. They shall be 
sent to the testing laboratory well packed in damp sand, damp sacks, or 
other suitable material so as to arrive there in a damp condition not less 
than 24 hours before the time of test. On arrival at the testing laboratory, 
the specimens shall be stored in water at a temperature of 27° ± 2°C until 
the time of test. Records of the daily maximum and minimum tempe- 
rature shall be kept both during the period of the specimens remain on 
the site and in the laboratory. 

4. SECURING AND PREPARING SPECIMENS OF 

HARDENED CONCRETE FOR COMPRESSION TEST 

4.1 This clause deals with the procedure for securing and preparing com- 
pression test specimens obtained from hardened concrete after the con- 
crete has been laid in position. 

4.2 The test specimens shad be procured from hardened concrete according 
to the method described in 4 of IS: 1199-1959.* 

4.3 Cores to be tested for compression strength shall have ends that are 
reasonably even, perpendicular to the axis and of the same diameter as 
the body of the specimen. A core which, before capping, has a maximum 
height of less than 95 percent of the diameter, or after capping, a height 
less than its diameter shall not be used. 

4.4 Capping — The ends of the specimen shall be capped before testing. 
The material used for the capping shall be such that its compressive 
strength is greater than that of the concrete in the core. Caps shall be 
made as thin as practicable and shall not flow or fracture before the con- 
crete fails when the specimen is tested. The capped surfaces shall be at 
right angles to the axis of the specimen and shall not depart from a plane 
by more than 005 mm. The capping of specimens shall be carried out 
as described in 2.11. 

4.5 After checking for irregularities, the core shall be placed in water at a 
temperature of 24° to 30°C for 48 hours before testing. The overall height 
of the specimens, with capping shall be measured to the nearest millimetre. 

'Since revised. 

10 



IS: 516- 1959 

5. TEST FOR COMPRESSIVE STRENGTH OP 
CONCRETE SPECIMEN 

5.1 This clause deals with the procedure for determining the compressive 
strength of concrete specimens. 

5.2 Apparatus 

5.2.1 Testing Machine — The testing machine may be of any reliable 
type, of sufficient capacity for the tests and capable of applying the load 
at the rate specified in 5.5. The permissible error shall be not greater 
than ± 2 percent of the maximum load. The testing machine shall be 
equipped with two steel bearing platens with hardened faces. One of the 
platens (preferably the one that normally will bear on the upper surface 
of the specimen) shall be fitted with a ball seating in the form of a portion 
of a sphere, the centre of which coincides with the central point of the 
face of the platen. The other compression platen shall be plain rigid 
bearing block. The bearing faces of both platens shall be at least as large 
as, and preferably larger than the nominal size of the specimen to which 
the load is applied. The bearing surface of the platens, when new, shall 
not depart from a plane by more than 0-01 mm at any point, and they 
shall be maintained with a permissible variation limit of 0-02 mm. The 
movable portion of the spherically seated compression platen shall be held 
on the spherical seat, but the design shall be such that the bearing face 
can be rotated freely and tilted through small angles in any direction. 

5.3 Age at Teat — Tests shall be made at recognized ages of the test 
specimens, the most usual being 7 and 28 days. Ages of 1 3 weeks and one 
year are recommended if tests at greater ages are required. Where it may 
be necessary to obtain the early strengths, tests may be made at the ages 
of 24 hours ± J hour and 72 hours + 2 hours. The ages shall be cal- 
culated from the time of the addition of water to the dry ingredients. 

5.4 Number of Specimens — At least three specimens, preferably from 
different batches, shall be made for testing at each selected age. 

Note — When a full investigation is being carried out. it is advisable for three 
separate batches to be made for each given variable. An equal number of speci- 
mens for each variable should lie made. 

5.5 Procedure — Specimens stored in water shall be tested immediately 
on removal from the water and while they are still in the wet condition. 
Surface water and grit shall be wiped off the specimens and any projecting 
fins removed. Specimens when received dry shall be kept in water for 
24 hours before they are taken for testing. The dimensions of the speci- 
mens to the nearest 0-2 mm and their weight shall be noted before testing. 

5.5.1 Placing the Specimen in the Testing Machine — The bearing surfaces 
of the testing machine shall be wiped clean and any loose sand or other 
material removed from the surfaces of the specimen which are to be in 

11 



IS: 516 -1959 

contact with the compression platens. In the case of cubes, the specimen 
shall be placed in the machine in such a manner that the load shall be ap- 
plied to opposite sides of the cubes as cast, that is, not to the top and 
bottom I he axis of the specimen shall be carefully aligned with the 
centre of thrust of the spherically seated platen No packing shall be 
used between the faces of the test specimen and the steel platen of the 
testing machine As the spherically seated block is brought to bear on 
the specimen, the movable portion shall be rotated gently by hand so 
that uniform seating may be obtained. The load shall be applied without 
shock and increased continuously at a rate of approximately 140 kg/sq 
cm/min until the resistance of the specimen to the increasing load breaks 
down and no greater load can be sustained. The maximum load applied 
to the specimen shall then be recorded and the appearance of the concrete 
and any unusual features in the type of failure shall be noted. 

5.6 Calculation — The measured compressive strength of the specimen 
shall be calculated by dividing the maximum load applied to the specimen 
during the test by the cross-sectional area, calculated from the mean di- 
mensions of the section (see also 4.5.1 of IS- 1199-1959) and shall be 
expressed to the nearest kg per sq cm. Average of three values shall be 
taken as the representative of the batch provided the individual variation 
is not more than + IS percent of the average. Otherwise repeat tests 
shall be made. 

5.6.1 A correction factor according to the height/diameter r*tio of 
specimen after capping shall be obtained from the curve shown in Fig. 1. 
The product of this correction factor and the measured compressive 
strength shall be known as the corrected compressive strength, this being 
the equivalent strength of a cylinder having a height/diameter ratio of two. 
The equivalent cube strength of the concrete shall be determined by 
multiplying the corrected cylinder strength by 5/4 

5.6.2 Report — The following information shall be included in the report 
on each test specimen: 

a) identification mark, 

b) date of test, 

c) age of specimen, 

d) curing conditions, including date of manufacture of specimen in 
the field, 

e) weight ot specimen, 

f) dimensions of specimen, 

g) cross-sectional area, 
h) maximum load, 

]) compressive strength, and 
k) appearance of fractured faces of concrete and type of fracture, 

if the se are unusual. 
•Since revised 

1Z 



IS: 516 -1959 



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6. DETERMINATION OF COMPRESSIVE 

STRENGTH OF CONCRETE USING PORTIONS Of 
BEAMS BROKEN IN FLEXURE ( " EQUIVALENT 
CUBE " METHOD ) 

6.1 This clause specifies tlio procedure for determining the compressive 
strength of concrete using portions of beams broken in flexure as the test 
specimens. The results obtained from this test are approximately equal to, 
and on the average may be up to 5 percent greater than those obtained 
by the test specified in 5. 

Note - For method of nuikinn and t«iUing flexure test spi omens, see 7. 

6J Apparatus 

6.2.1 Compression Testing Machine — The testing machine shall comply 
in all respects with the requirements of 5.2.1. 

6.2 J Bearing Plates — Two metal bearing plates not less than 6-5 mm 
or more than 19 mm thick shall be provided. The plates shall be 10 cm 
square for the beams 10 cm in depth and 15 cm square for the beams 15 cm 
in depth with the surfaces machined to a permissible variation not 
exceeding 002 mm. The distance between the opposite edges shall be 
the specified size ± 002 mm and the angle between the edges shall be 
90° ± 0-5°. 



13 



18:516-1959 

6.3 Test Specimens — The length of the broken portions of the beams 
selected for the compression test shall be at least 5 cm greater than the 
depth of the beam and the broken portions shall be free from cracks, 
chipped surfaces or other obvious defects within the length to be tested. 

6.4 Procedure — During the interval between testing the specimens as 
beams and testing the broken portions as cubes, the specimens shall be 
stored in water at a temperature of 24° to 30°C and shall be tested im- 
mediately on removal from the water and while still in the wet condition. 

6.4.1 Placing the Specimen in the Testing Machine — The bearing sur- 
faces of the testing machine and the bearing plates shall be wiped clean 
and any loose sand or other material shall be removed from the surfaces 
of the specimen which are to be in contact with the bearing plates. The 
specimen shall be placed between the bearing plates in such a manner 
that the upper bearing plate is directly over the lower plate and the bear- 
ing plates extend at least 25 mm from each end of the specimen. A device 
which ensures the proper location of the upper plate with reference to the 
lower plate is shown in Fig. 2. No packing shall be used between the 
faces of the specimen and the bearing plates. The specimens shall be 
tested with the moulded sides in contact with the plates Thr load shall 



cuioe SUPPORT 

6OLTE0 OR WELOEO 
TO BOTTOM PLATE 




TOP BEARING 

PLATE 



BOTTOM BEARING 
PLATE 



Fig 2 Devici- for Alignino Blarinc Plmes 
14 



IS : Sit . 1*59 

be applied without shock and increased continuously at a rate of approxi- 
mately 140 kg/sq cm/min until the resistance of the specimen to the in- 
creasing load breaks down and no greater load can be sustained. The 
maximum load applied to the specimen shall then be recorded and the 
appearance of the concrete and any unusual features in the type of failure 
shall be noted. 

6.5 Calculation — The equivalent cube strength of the specimen shall 
be calculated by dividing the maximum load by the area of contact of 
the bearing plates and shall be expressed to the nearest kg/sq cm. 

6.6 Report — The following information shall be included in the report 

on each specimen: 

a) identification mark, 

b) date of test, 

c) age of specimen, 

d) curing conditions, 

e) nominal size of specimen, 

f) maximum load, 

g) equivalent cube strength, and 

h) appearance of the concrete and type of fracture, if these are unusual. 

7. MAKING AND CURING FLEXURE TEST 
SPECIMENS IN THE LABORATORY 

7.1 This clause specifies the procedure for making and curing flexure test 
specimens of concrete in the laboratory where accurate control of the 
quantities of materials and test conditions is possible, provided the maxi- 
mum nominal size of the aggregate does not exceed 38 mm. The method 
is specially applicable to the making of preliminary flexure tests to ascertain 
the suitability of the available material or to determine suitable mix 
proportions. 

7.2 Sampling of Material — Preparation of materials, proportions, 
weighing, mixing of concrete shall be done in the same way as in the case 
of making compression test specimens in the laboratory (see 2). 

7 .3 Size of Specimens — The standard size shall be 15 x 15 x 70 cm. 
Alternatively, if the largest nominal =>i/e of the aggregate docs not exceed 
19 mm, specimens 10 x 10 x 50 cm may be usecL 

7.4 Apparatus 

7.4.1 The mould shall be of metal, preferably steel or cast iron and the 
metal shall be of sufficient thickness to prevent spreading or warping. 
The mould shall be constructed with the longer dimension horizontal and 
in such a manner as to facilitate the removal of the moulded specimens 

15 



18:516-1959 

without damage. The mould shall be u> machined that when assembled 
ready for use the dimensions shall be accurate within the following limits: 

a) The height of the mould shall be either 15-0 ± 0-005 cm or 
10-0 ± 0-005 cm, and the corresponding internal width of the 
mould shall be 15-0 ± 0-02 cm or 10-0 ± 0-02 cm respectively. 
The angle between the interior faces and the top and bottom 
planes of the mould shall be 90° ± 0-5°. The internal surfaces of 
the mould shall.be plane surfaces with a permissible variation of 
0-02 mm in 15-0 cm and 0-1 mm overall. 

b) Each mould shall be provided with a metal base plate and two 
loose top plates of 4-0x0-6 cm cross-section and 5-0 cm longer than 
the width of the mould. The base plate and top plate shall have 
plane surfaces with a permissible variation of 0-05 mm. The base 
plate shall support the mould without leakage during the filling, 
and shall be rigidly attached to the mould. 

c) The parts of the mould when assembled shall be positively and 
rigidly held together, and suitable methods of ensuring this, both 
during the filling and on subsequent handling of the filled mould, 
shall be provided. 

d) In assembling the mould for use, the joints between the sections 
of the mould shall be thinly coated with mould oil and a similar 
coating of mould oil shall be applied between the contact surfaces 
of the bottom of the mould and the base plate in order to ensure 
that no water escapes during the filling. The interior faces of the 
assembled mould shall be thinly coated with mould oil to prevent 
adhesion of the concrete. 

7.4.2 Tamping Bar — The tamping bar shall be a steel bar weighing 
2 kg, 40 cm long, and shall have a ramming face 25 mm square. 

7.5 Procedure, curing, age at test, number of specimens shall be the same 
as in 2 and 5. 

8. TEST FOR FLEX URAL STRENGTH OF 
MOULDED FLEXURE TEST SPECIMENS 

8.1 This clause deals with the procedure for determining the flexural 
strength of moulded concrete flexure test specimens. 

8.2 Apparatus 

8.2.1 The testing machine may be of any reliable type of sufficient 
capacity for the tests and capable of applying the load at the rate specified 
in 8.3. The permissible errors shall be not greater than ± 0-5 percent 
of the applied load where a high degree of accuracy is required and not 
greater than ±1-5 percent of the applied load for commercial type of use. 
The bed of the testing machine shall be provided with two steel rollers, 

16 



IS: 516- 1959 

38 mm in diameter, on which the specimen is to be supported, and these 
rollers shall be so mounted that the distance from centre to centre is 60 cm 
for 15-0 cm specimens or 40 cm for 100 cm specimens. The load shall be 
applied through two similar rollers mounted at the third points of the 
supporting span, that is, spaced a f 20 or 13-3 cm centre to centre. The load 
shall be divided equally between the two loading rollers, and all rollers 
shall be mounted in such a manner that the load is applied axially and 
without subjecting the specimen to any torsional stresses or restraints. 
One suitable arrangement which complies with these requirements is 
indicated in Fig. 3. 

8.3 Procedure — Test specimens stored in water at a temperature of 
24° to 30°C for 48 hours before testing, shall be tested immediately on 
removal from the water whilst they are still in a wet condition. The di 
mensions of each specimen shall be noted before testing No pieparation 
of the surfaces is required. 

8.3.1 Placing the Specimen in the Testing Machine - The bearing sur- 
faces of the supporting and loading rollers shall be wiped cUan, and any 
loose sand or other material removed from the surfaces of the specimen 
where thev are to make contact with the rollers. The specimen shall then 
be placed in the machine in such a manner that the load shall be applied to 
the uppermost surface as cast in the mould, along two line* spaced 200 or 
13-3 cm apart. The axis of the specimen shall be carefully aligned with 
the axis of the loading device. No packing shall be used between the 
bearing surfaces of the specimen and the rollers. The load shall be applied 
without shock and increasing continuously at a rate such that the extreme 
fibre stress increases at approximately 7 kg/sq cii./min, that is, at a 
rate of loading of 400 kg/min for the 15-0 cm specimens and at a rate of 
180 kg/min for the 10-0 cm specimens. The load shall be increased until 
the specimen fails, and the maximum load applied to the specimen during 
the test shall be recorded. Th«" appearance of the fractured faces of con- 
crete and any unusual features in the type of failure shall be noted. 

8.4 Calculation — The flexural strength of the specimen shall be ex- 
pressed as the modulus of rupture f h , which, if ' a ' equals the distance 
between the line of fracture and the nearer support, measured on the 
centre line of the tensile side of the specimen, in cm, shall be calculated 
to the nearest 0-5 kg/sq cm as follows: 

fh ~ b ■ d* 

when ' a ' is greater than 200 cm for 150 cm specimen, or greater than 
13-3 cm for a 10-0 cm specimen, or 

3/k - a 
Jb ~ b'd* 
when ' a ' is less than 200 cm but greater than 170 cm for 150 cm speci- 
men, or less than 13-3 cm but greater than 110 cm for a 100 cm specimen 

17 



IS : 516 - 1959 

where 

b = measured width in cm of the specimen, 

i = measured depth in cm of the specimen at the point of 
failure, 

/ ~ length in cm of the span on which the specimen was sup- 
ported, and 

p — maximum load in kg applied to the specimen 

If ' a ' is less than 17-0 cm for a 15-0 cm specimen, or less than 11-0 cm 
for a 10-0 cm specimen, the results of the test shall be discarded 

8.5 Report — The following information shall be included in the report 
on each specimen: 

a) identification mark, 

b) date of test, 

c) age of specimen, 

d) curing conditions, 

e) size of specimen, 

f) span length, 

g) maximum load, 

h) position of fracture ( value ' a ' ), 

j) modulus of rupture ( kg per sq cm ), and 

k) appearance of concrete and type of fracture if these are unusual 

9. DETERMINATION OF THE MODULUS OF 

ELASTICITY BY MEANS OF AN EXTENSOMETER 

9.1 This clause specifies the procedure for making and curing test speci- 
mens, determining the modulus of elasticity of concrete in compression 
by means of an extensometer where the maximum nominal size of aggre- 
gate does not exceed 38 mm. 

9.2 Size of Specimens — The test specimens shall consist of concrete 
cylinders 15-0 cm in diameter and 30-0 cm long. Alternately, other sizes 
of cylinders or square prisms may be used provided that the height/dia- 
meter or height/width ratio is at least 2 

9.3 Sampling, apparatus and procedure shall be as described in 2. 

9.4 Preparation of Test Specimens — The test specimens shall be pre- 
pared in accordance with 2 and shall be stored in water at a temperature of 
24° to 30°C for at least 48 hours before testing At least three specimens 
shall be made and tested. 

9.5 Age at Test — Normally test shall be made when the specimens 
reach the age of 28 days 

18 



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Fig. 3 Arrangement for Loading or Flexure Test Specimen 




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<6 



IS: 516- 1959 

9.6 In order to determine the compressive strength of the concrete, three 
test specimens for compressive strength shall be made together with each 
set of cylinders or prisms in accordance with 9.2. The test specimens for 
compressive strength shall be made from the same sample of concrete as 
the cylinders or prisms and shall be cured and stored under identical 
conditions. 

9.7 Apparatus 

9.7.1 Testing Machine — The testing machine shall comply in all 
respects with the requirements of 5.2.1 and in addition shall be capable 
of maintaining the load at any desired value. 

9.7.2 Extensometers — Two extensometers are required each having a 
gauge length of not less than 10-2 cm and not more than half the length 
of the specimen. They shall be capable of measuring strains to an accu- 
racy of 2 X 10"*. Mirror extensometers of the roller or rocker type are 
suitable. 

9.8 Procedure — The three test specimens for compressive strength shall 
first be tested in accordance with 5 and the average compressive strength 
shall be recorded. Immediately on removing the cylinder or prism 
from the water and while it is still in a wet condition, the exte- 
nsometers shall be attached at the ends, or on opposite sides of 
the specimen and parallel to its axis, in such a way that the gauge points 
are symmetrical about the centre of the specimen and in no case are nearer 
to either end of the specimen than a distance equal to half the diameter 
or half the width of the specimen. The extensometers shall be fixed with 
the recording points at the same end. The specimen shall be immediately 
placed in the testing machine and accurately centred. The load shall be 
applied continuously and without shock at a rate of 140 kg/sq cm/min 
until an average stress of (C-h5) kg sq cm is reached, wheie C is one- 
third of the average compressive strength of the cubes calculated to the 
nearest 5 kg/sq cm. The load shall be maintained at this stress for at 
least one minute and shall then be reduced gradually to an average stress 
of 1-5 kg/sq cm when extensometer readings shall be taken. The load 
snail be applied a second time at the same rate until an average stress of 
(C-+-T5) kg/sq cm is reached. The load shall be maintained at this figure 
while extensometer readings are taken. The load shall again be reduced 
gradually and readings again taken at 1-5 kg sq cm. The load shall then 
be applied a third time and extensometer readings taken at ten approxi- 
mately equal increments of stress up to an average stress of (C-t-1-5) kg/ 
sq cm. Readings shall be taken at each stage of loading with as little 
delay as possible. If the overall strains observed on the second and third 
readings differ by more than 5 percent, the loadiiig cycle shall be repeated 
until the difference in strain between consecutive readings at ((,' f IS) kg/ 
sq cm does not exceed 5 percent. 

20 



18:516-1959 

9.9 Calculation — The strains at the various loads in the last two cycles 
shall be calculated separately for each extensorneter and the results shall 
be plotted graphically against the stress. Straight lines shall be drawn 
through the points for each extensorneter; the slopes of these two lines 
shall be determined and from them the average value shall be found. If 
the difference between the individual values is less than 15 percent of the 
average value, this average value, expressed in kg/sq cm to the nearest 
1 000 kg/sq cm shall be recorded as the modulus of elasticity of the con- 
crete. If the difference is greater than 15 percent, the specimen shall be 
re-centred in the testing machine and the test repeated. If the difference 
after re-centring and testing is still greater than 15 percent of the average 
value, the results of the test shall be discarded. 

9.10 Report — The following information shall be included in the report: 

a) identification mark; 

b) date of test; 

c) age of specimen; 

d) shape and nominal dimensions of specimen ; 

e) modulus of elasticity; and 

f) remarks, such as number of loading cycles. 

10. DETERMINATION OF THE MODULUS OF 

ELASTICITY BY ELECTRODYNAMIC METHOD 

10.1 This clause specifies the procedure for determining the modulus of 
elasticity of concrete by an electrodynamic method, namely by measuring 
the natural frequency of the fundamental mode of longitudinal vibration 
of concrete prisms. This is a non-destructive test and therefore the same 
specimen 1 * may subsequently be used for the flexural strength test specified 
in 8. 

10.2 Specimens — The specimens bhall in all respects comply with the 
requirements of 9.2. 

10.3 Apparatus — The apparatus shall consist of the following. 

10.3.1 A variable frequency oscillator with a working range up to 
10 000 cycles per second, reading to an accuracy of ±0-5 percent. A means 
of varying the output power shall be incorporated, and the output power 
shall be not less than 2 watts. 

10.3.2 An electro-magnetic exciter unit of the moving-coil or variable 
air-gap type. If the moving-coil type is used, the former and coil should 
have as low an inertia as possible, the mass being not more than 0-2 percent 
of the mass of the specimen ( the former should be of light card or paper ). 
A suitable type of instrument is shown in Fig. 4. If a variable air-gap 
exciter unit is used, this shall be of a similar type to the pick-up unit. 

21 



8 



SPECIMEN 



•KK>UP UNIT 



~\ 



UCHT MM* FOMKR. THE FORMER 

ANO COM. MUST SLIDE LOOSELY IN 

THE ANNULAR SPACE BETWEEN THE 

POLES OF THE MAGNET 

CLAMP OP SOPPOPT 



EXCITER 




VA\V\\V\\VvVVV\\VAVsA 



NOT TO EICEEO jgl* LENGTH 
OP SPECIMEN 




ADHESIVE 




aVs^aVavCv 



I / I /COIL C# SO TO lOO TURNS 




DETAIL OF EXCITER 

•The adhesive or other method of attachment should preferably allow paper cylinder to be detached after 
teat for further oae. 



0B 



i 



fic. 4 aftftamgemekt of specimen for the determination of modulus of 
Elasticity »y Rlectrodykamic Method 



IS: 516- 1959 

10.3.3 An electro-magnetic pick-up unit ol the ordinary telephone type. 
Alternatively, a piezo-clcctric gauge may be used, provided that its mass 
\S not more than 0-2 percent of the mass of the specimen. 

10.3.4 An audio-frequency amplifier. 

10.3.5 An amplitude indicator consisting of a voltmeter, millianimrter 
or cathode-ray oscilloscope. 

10.3.6 A fixed clamp or support with a maximum width of t \\X\ of the 
length of the specimen. If a variable air-gap exciter unit is used in con- 
I unction with a variable air-gap pick-up, the support shall he metallic 
arid earthed. 

10.4 Procedure — Immediately on removal from water, except when 
the specimen is less than 24 hours. old, and while still in a wet condition, 
the specimen shall be clamped or balanced at its centre on the fixed sup- 
port. Where a moving-coil type of exciter unit is used, the moving-coil por- 
tion shall be fixed to the middle of one end face of the specimen as indicated 
in Fig. 4. It may be fixed to the specimen by means of resin or other 
suitable adhesive. The resin can conveniently be applied with an electric 
soldering iron. A disk of tinfoil, of 5 cm diameter, shall be lightly greased 
to ensure adhesion and placed on the centre of the other end of the speci- 
men, and the pick-up unit shall be placed with thr diaphragm as close 
as possible to the foil but the pick-up unit shall not be allowed to touch 
the tinfoil or the specimen. If a variable air-gap exciter is used, this shall 
be mounted in a. similar manner to the pick-up, using a disk of tinfoil. 
The exciter unit shall be driven by the variable frequency oscillator, and 
the oscillations received by the pick-up unit shall be amplified bv the 
audio-frequency amplifier and applied to the indicator in such a manner 
as to show the amplitude of the oscillations received. The frequency of 
excitation shall be varied until resonance is obtained in the fundamental 
mode of longitudinal vibration. The frequency shall be recorded as the 
natural frequency of the fundamental mode of longitudinal vibration. 

Note - ■ Resonance is indicated by a maximum deflection of the indicator, but 
teverat mamma may I* obtained, and experience is necessary to know which in the 
maximum required Frequencies within + 10 percent of the expected value, 
which may be calculated Irom the formula given in 10.6 should be investi- 
gated Values ol Ihe modulus of elasticity range from 1 4 X 10* kg/sq cm for low- 
qualttv concretes at earl> axes to 5 x 10* kg/sq cm for high-quality concretes .it 
greater ages This represents a frequent \ ra'nge of U5O0O7/ cycles per second to 
2230007/ cycles per second where I n the length ol the specimen in cm It it usually 
possible to obtain resonance also at the Irequi-nry of the first harmonic which 
is twice the fundamental frequency and these two conditions arc normally the 
most well defined 

10.5 Measurement! - The following measurements shall be made on 
the specimen : 

a) Weight — The wet specimen shall be weighed to an accuracy of 
0-25 percent. 

23 



18: 516 . 1959 

b) Length — The length of the specimen shall be determined to .in 
accuracy of ± 1 mm, the average being taken of at least four »ym- 
meirically placed measurements. 

c) Depth and Breadth — The average depth and breadth of the speci- 
men shall be determined to an accuracy of + 0-2 mm, the average 
being taken in each case of at least six measurements rpac d 
equally along the length of the specimen. 

10.6 Calculation — The density of the wet concrete shall be calculated 
from the formula: 

- l0 ** w 
w ~ Ixbxd 

10.6.1 The dynamic modulus of elasticity shall then be calculated to 
the nearest 1 000 kg/sq cm from the formula : 

£-4083 X 10r B n*Pw 

where 

E = dynamic modulus of elasticity in kg per sq cm, 

n — natural frequency of the fundamental mode of longitudinal 

vibration of the specimen, in cycles per second, 
w = density in kg per cu m, 
W = weight in kg of the specimen, 
/ = length in cm of the specimen, 
b = breadth in cm of the specimen, and 
d = depth in cm of the specimen. 

10.7 Number of Specimens — At least three specimens shall be tested 
for each age of test. 

10.8 Report — The following information shall be included in the report 
on each specimen : 

a) identification mark, 

b) date of test, 

c) age of specimen, 

d) curing conditions, 

e) average dimensions of specimen, 

f) weight of wet specimen. 

g) natural frequency of the fundamental mode of longitudinal vibration 
of specimen, and 

h) dynamic modulus of elasticity. 



24 



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